Papers by Keyword: Formability

Abstract: The aim of this work is to analyze the effect of the anisotropy on the formability of the third generation of advanced high strength steel (3genAHSS) from experimental and theoretical point of view. The reference material is the USS CR980XG3TM️ AHSS, a 3genAHSS 980T/600Y-retained austenite bearing-high elongation steel grade. A careful experimental work on the selected 3genAHSS characterization has been performed. The anisotropy factors and the yield stresses have been identified from tensile tests at several orientations with respect to the rolling direction. The experimental forming limit diagram under linear strain paths has been determined using Nakajima tests and the Erichson test for the equibiaxial stretching, respectively. The Marciniak-Kuczynski analysis is used to simulate the onset of localized necking through an advanced sheet metal forming limit model. YLD00-2d yield condition gives the initial shape of the yield locus. Swift strain–hardening power law is used to describe the strain hardening of the material. The effect of the anisotropy on the forming limits of 3genAHSS steel is analyzed. It was achieved proper reproducibility of the experimental tendencies of anisotropic factor distribution and the yield stress as a function of the tensile loading axis by the selected constitutive equations. A good accuracy of the FLDmodel on the prediction of the experimental results is found.

Abstract: Reliable composite forming experiments are required to characterize composite formability, to aid material development, and to validate process simulations models. Due to practical reasons, however, typically a limited amount of forming configurations is studied. The objective of this study is, therefore, to develop a methodology for obtaining controlled forming results in a wide range of configurations. Press forming experiments using a dome geometry were used to explore the formability of two commercial unidirectional thermoplastic composite materials. A variety of forming configurations was employed by changing the blank dimensions and layup. The observation of wrinkling defects was simplified by leaving an additional 3 mm tool gap. Blank width and layup had the most influence on the wrinkling severity, followed by blank thickness and length. Quasi-isotropic layups were found to produce wrinkles in nearly all cases, confirming a difficulty in general to form double curved parts. The size and number of wrinkles in these layups were found to change with the stacking sequence. Cross-ply layups showed better formability, but significant wrinkles were still observed depending on the orientation of the blank relative to the layup. The formability experiments using a dome geometry provided a reliable methodology for controlled forming results in many configurations using a generic toolset. Additionally, a comprehensive comparison of formability for two commercial thermoplastic UD materials in a variety of scenarios was provided.

Abstract: Fine blanking is a key technology for the near-net-shape production of sheet metal components. It is often used in combination with processes such as deep drawing. With increasing environmental requirements, the processing of materials with lightweight construction potential is becoming more and more important. A group of materials with high potential for lightweight construction, not only due to their suitability for hot stamping, is the group of manganese-boron steels. The fine blanking properties of these steels have not yet been exhaustively investigated. In this work, the fine blanking properties of the manganese-boron steel 40MnB4 were investigated in comparison to the quenched and tempered steel 42CrMo4. This was done using a star-piece fine blanking layout with investigation of die roll as well as tooth tip cracking. Furthermore, an investigation of the high-temperature fine blanking properties were investigated by means of inductive heating prior to fine blanking. The process forces were evaluated depending on the sheet metal temperature. A good fine blanking capability of 40MnB4 could be confirmed. Process forces and product quality were comparable to 42CrMo4 steel. Accordingly, an industrial application of fine blanking to manganese-boron steels seems highly promising.

Abstract: Titanium alloys are widely used in aerospace and automotive industries due to their excellent mechanical properties, however, the formability is limited, which is an issue during forming. In the present study, the effect of temperature and strain rate on the tensile properties of the titanium α-alloy KS1.2ASN was investigated. It was observed that there is initially no gain in ductility with increase in temperature until 400 °C, however, maximum formability is reached at maximum tested temperature of 600 °C. EBSD analysis revealed that twinning is the main deformation mechanism at room temperature, however, sliding deformation becomes more pronounced with increasing temperature. An increase in strain rate leads to a decrease in elongation, but the influence is less pronounced compared to temperature.

Abstract: An area in the automotive industry that receives a lot of attention today is the introduction of lighter and more advanced material grades in order to reduce carbon emissions, both during production and through reduced fuel consumption. As the complexity of the introduced materials and component geometries increases, so does the need for more complex failure prediction approaches. A proposed path-independent failure criterion, based on a transformation of the limit curve into an alternative evaluation space, is investigated. Initially, the yield criterion used for this transformation of the limit curve was investigated. Here it was determined that the criterion for the transformation could not be decoupled from the material model used for the simulation. Subsequently, the approach using the transformed limit curve was tested on an industrial case from Volvo Cars, but a successful failure prediction was not obtained.

Abstract: A Micro forming was primarily developed in order to view the usage and significance of micro metal forming technology. It is implemented for the manufacturing and production of micro metallic devices like micro pump, micro gears (Polyoxymethylene polymer), Biodegradable implants (Polylactic acid) etc. The die assembly is provided with a DLC (Diamond like coating) coating during work study to resolved small size dimensional accuracy issue and enhanced tribological properties. Various High Energy Metal Forming processes (HERF) is discussed like ultrasonic vibration, explosive forming, magnetic forming, electro hydraulic forming, ultrasonic vibration and heating process for enhancement in formability and accuracy to the product of micro scale dimension. The detailed review of Micro forming and its applications in various fields that utilized the various high energy processes is discussed in this paper. Keywords: Biodegradable, Tribological Properties, HERF (High Energy Rate forming), Formability.

Abstract: Utilizing the common sheet metal forming method has many challenges in the field of sheet metal forming. Higher product quality with the lower quantities is an important requirement in this manufacturing field. The incremental forming process (IPF) is an innovation technology that can satisfy these requirements. In this paper, the single point incremental forming (SPIF) with different roller ball tool was researched. The results show that the smaller ball could provide a better product quality. However, the bigger ball could create a deeper geometry

Abstract: Dual-pressure tube hydroforming (THF) is a tube hydroforming process variant whereby deformation of the tubular specimen is achieved by exerting fluid pressure on both the inside and outside surfaces of the tube. Dual-pressure THF experiments are conducted to study tribological conditions when producing pear-shaped and triangular parts. The pressure-loading paths are designed to exert pressure in oscillatory pattern: I.e., the pressure on the inside was alternated with pressure on the outside causing the tube to expand and contract/buckle as deformation progressed. During tube contraction, the metal-to-metal contact area is substantially reduced. This leads to reduction in friction stress at the tube-die interface, thus increasing formability. Comparing the geometries of the formed parts produced by dual-pressure THF and conventional THF reveals that the former results in a substantial increase in the protrusion height of a pear-shaped specimen.

Abstract: Recently the high strength steel has been applied in the automotive more and more widely. In this study, the effect of blank shape on the formability of an automotive part was analyzed. The three kinds of blank shapes were chosen, including a rectangular shaped blank, a blank with two corners cut straightly and a blank with two corners cut in curve. The effect of the variable blank holder force on the formability was studied. The four kinds of variable blank holder force were applied. The blank shape in this part is the blank with two corners cut curve. The results show that the blank with two corners curve is the most suitable. And the blank holder force from 1000 kN to 1500 kN is the most useful for the formability.

Abstract: While Incremental Sheet Forming (ISF) is approaching accuracy levels suitable for industrial take-up for specific applications, limited forming angles are still a great concern, leaving many applications out of reach. In this paper a two sided strategy for multistep incremental forming is presented, aiming at increased uniform wall thickness. By sequentially forming steeper wall angles, alternating passes between front and back side of the sheet, wall angles up to 105.5° were successfully reached in AA3103 with a blank thickness of 1.5mm. A resulting minimal thickness of 0.4mm and thickness range of 0.2mm was achieved for the 105.5°part.